The following patent is noted and the teachings thereof are hereby incorporated by reference: U.S. Pat. No. 6,768,803, to Duhamel, issued Jul. 27, 2004 for a “METHOD AND APPARATUS FOR SELECTIVE ACOUSTIC SIGNAL FILTERING.”
It is well known that noise in the work place can both mask important audio “information” and cause permanent physical damage to the human “hearing” system. For example, in the heavy construction industry, the wearing of sound blocking “ear muffs” is a common solution. The problem also exists in the performing arts arena, particularly in the “loud” jazz and heavy rock music communities. The normal solution is to use earplugs, which are small, rubbery or foam devices that are inserted into the ear channel to “block” the sound. However, such devices tend to block out or attenuate all of the acoustic signals, thereby reducing or eliminating certain signals to a level where they cannot be heard or appreciated by the listener.
A similar problem exists in the classical music industry as James R. Oestrich suggests in an article published on Jan. 11, 2004 in the New York Times. Auditory acuity and sensitivity are especially important to the musician and even a subtle hearing deficit may detract from the musician's performance, and in extreme cases, severe hearing loss could mean an end to a performing career. The Occupational Safety and Health Administration (OSHA) regulates noise levels in the workplace and exposure levels within the Orchestra may not exceed an 8 hour Time Weighted Average (TWA) of 90 dBA. The ceiling level is 115 dBA, meaning that and at no time may this level be exceeded 115 dBA. Exposure to excessive sound levels can cause damage in two ways: mechanical trauma and sensorineural hearing loss. Sensorineural hearing loss, caused by repeated exposure to excessive noise levels, is of most concern to musicians. In addition to the auditory effects, noise can cause physiological and/or psychological problems as well. The physiological effects may include a wide variety of symptoms including increased heart rate, blood pressure, breathing rate, muscle contractions and perspiration. Psychological complaints may include nervousness, tension, anger and irritability.
However, this problem has not been addressed due to the inherent limitations of conventional hearing aids or ear plugs, including lack of control as to the amount of attenuation desired by a listener, as well as a control over the directionality of the attenuation. In other words, performers may wish to more heavily attenuate the percussion or brass section behind them, but to keep the woodwinds to the side or strings in front of them at a higher or non-attenuated level. In any live musical performance, it is critical to “hear” exactly what is going on around you. This may be for better balance, a matching of tonal quality, a “clue” as to when to play, etc. Not only is this “audio information” important, but so is the location or direction from which it is coming.
As mentioned above, the problem with the conventional ear muff and ear plug approaches is that not only is the quality of the sound changed, but that any directionality is lost. The present invention is, therefore, directed to an improved or “smart” ear plug (in the ear or not), that provides true acoustic rendition of the sound, wherein the amplitude or similar signal characteristics of the acoustic signal may be controlled on a directional basis.
The advent of micro-electronics provides new options for the sensing and delivery of acoustic information or signals. Micro-electronics makes physically small circuitry and electromechanical systems possible. In accordance with one aspect of the present invention, there is provided an array of very small micro-electromechanical systems (MEMS) microphones to detect the acoustic waves or vibrations coming from a plurality of directions (e.g., front/rear, left/right side, above, below, etc.). Having received the various, discrete signals from the array of MEMS microphones, with their inherent directionality; a similar array of MEMS speakers or “audio transducers”, could be used to generate the output (perhaps conditioned to attenuate the signal from certain directions more than other directions). Thus, the system would provide a user with all of the audio information, but with selective attenuation (or gain) based upon directionality of the acoustic source—providing the impression of being from the same direction with the same audio information but at a user adjustable sound level.
In accordance with the present invention, there is provided an acoustic control apparatus, comprising: input sensor for receiving an input acoustic signal to be processed, said input sensor including a microphone array, said microphone array manifesting vibration in response to interaction with the input acoustic signals from a plurality directions to generate a plurality of input signals, each representing an acoustic input from one of the plurality of directions relative to said input sensor; a signal processing device for producing, in response to the input signals, at least one output signal, said signal processing device characterized by a uniform frequency response such that the output acoustic signal spectrum level is generally reflective of an input acoustic signal spectrum level, said signal processing device further including a mixing circuit to enable a mixing of at least two acoustic signals from the plurality of directions; and an acoustic output port for generating the output acoustic signal produced by said signal processing device.
In accordance with another aspect of the invention, there is provided an acoustic signal processing system for processing acoustic signals in accordance with a user preference, comprising: at least one microphone array, said microphone array generating a plurality of input signals in response to acoustic vibrations, each input signal representing an acoustic input from one of a plurality of directions relative to said microphone array; a signal processing device for producing, in response to the plurality of input signals, at least one output signal, said signal processing device characterized by a uniform frequency response such that an output acoustic signal spectrum level is generally reflective of an input acoustic signal spectrum level, said signal processing device further including a mixing circuit with a crossover network, responsive to the user preference, to mix at least two acoustic signals from the plurality of directions; and at least one speaker for generating the output acoustic signal in response to the output signal from said signal processing device.
In accordance with a further aspect of the invention, there is provided a method for controlling the sound perceived by a user, comprising: receiving, using a micro-electronic microphone array, an input acoustic signal and generating a plurality of input signals representing the acoustic input from each of a plurality of directions relative to the array; processing the input signals to produce at least one output signal such that the output signal spectrum level is generally reflective of an input acoustic signal spectrum level, including mixing of at least two acoustic signals from the plurality of directions to produce the at least one output signal; and generating, by an output speaker responsive to the at least one output signal an acoustic signal directly in the canal of a user's ear.
The techniques described herein are advantageous because they provide a reduced-size method of controlling the audio or acoustic input received by a user, thereby enabling a user to function in an acoustically unfriendly environment without the complete loss or exclusion of acoustic information. The techniques of the invention are advantageous because they provide a range of alternatives, each of which is useful in appropriate situations. As a result of the invention, it is anticipated that musicians, construction workers and the like may find improved on-the-job experience and reduced hearing loss due to loud noises.
The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.